Dans la cuisine du Hérold Boulevard

Help me to find out what this vegetable (or fruit?) I bought in the street when I was searching for African products... The woman I bought it from told me many things about it : this is a sort of plum but also a vegetable, as oily as an avocado but an avocado mustn't be cooked, it is massively grown in Africa and help fighting the famine... It was only sold with street peddling, street vendors had big bag filled up with it... What is true ? What is wrong ? What is it ?! Please share this article and let find out the answer !